During implant surgery and in particular the implantation of a hip prosthesis, it has long been known to cement the prosthesis to the bone. In order to cement the prosthesis to the bone, the bone canal is broached or reamed to the desired shape to match the shape of the prosthesis anchoring portion. An anchoring portion of the prosthesis is then inserted, for example into the broached femoral bone to replace the natural ball portion of the hip bone.
In order to fix the anchoring portion to the long bone, it has been known to use cements such as polymethylmethacrylate (PMMA) which is inserted into the bone canal and packed upon the prosthesis prior to insertion of the prosthesis. These cements such as PMMA then anchor the anchoring portion of the prosthesis to the bone material.
In order to provide for a secure joint between the prosthesis and bone at the cement interface, it is desired to have the cement completely surround the prosthesis in the interstices between the prosthesis and the bone material. However, the insertion forces required to insert the implant often drive the cement substance down into the intramedullary canal and away from the fixation site. In this way, voids are formed in the cement mantle which later become stress points leading to early failure of the devices.
In order to address this concern, intramedullary devices such as plugs have been developed by manufacturers of implants in order to restrict the flow of the bone cement further into the intramedullary canal than is desired. Thus, when the implant is forced into the broached portion of the intramedullary canal the tendency of the thick bone cement to flow down the canal is prevented by the presence of blockage in the form of an intramedullary bone plug.
For example U.S. Pat. No. 4,245,359 shows a plug made of a plastic material which acts as a cement barrier for openings produced by operative procedures. The plug is clamped between the side walls of the opening by means of elastic flanges which prevent bone cement from escaping downward upon insertion of a stem portion. U.S. Pat. No. 4,293,962 shows a device for plugging the medullary canal in joint replacement surgery technique. The plug prevents the cement used for fixation from extending beyond the point where it is useful. The device is comprised of a tapered cylindrical plug which is threadedly engaged to a flexible insertion shaft. The plug is lodged in the appropriate place in the canal and the plug is made of a bio-compatible material. U.S. Pat. No. 4,302,855 discloses a bone plug for use in the intramedullary canal of a bone. The bone plug includes a resilient body of medical grade material. The body has a smooth, blunt, rounded nose, a mid point joined to the nose and having a toroidal shape and upper, open-ended portion joined to the mid portion and defining a recess. The upper, open-ended portion is generally frusto-conical in nature and further defines a plurality of circumferential spaced petal-like elements.
U.S. Pat. No. 4,344,190 shows a pressure fit plug which prevents cement from penetrating down the canal. The plug is described as being capable of being made of biodegradeable material so that in time is dissolves away.
U.S. Pat. No. 4,447,915 describes a medullary canal plug which is formed of a deformable and expandable outer body having a jacket formed of a number of segments in a conical expansion body which is pulled into the outer body in order to expand the outer body.
U.S. Pat. No. 4,697,584 describes an inflatable intramedullary plug used to plug the open end of intramedullary bone canal. And U.S. Pat. No. 5,092,891 describes a cement plug for sealing the medullary canal of a bone. The plug is composed of biocompatible plastic and is comprised of a tubular body which is slit axially having an obturator plate located at the upper end of the body and a tapered conical plug that can be advanced through the lower end of the body into the interior of the body. This causes expansion and engagement of the plug within the intramedullary canal.